Small optoelectronic modules such as imaging devices sometimes employ optical assemblies that include lenses stacked along the device's optical axis to achieve desired performance. In some instances, as part of the fabrication process, wafers that form the stack are aligned and bonded together. The wafers may be attached to one another, for example, by glue or other adhesive. The glue, however, sometimes migrates to areas that can negatively impact optical performance.
Further, in some instances, relatively thin spacer wafers are used to separate various optical members in the stack from one another or to separate the optical assembly from other optoelectronic components in a module. The use of thin spacer wafers can be advantageous because it helps to reduce the overall height of the assembly or module. On the other hand, distortion of such wafers can occur during processing. Further, the spacer wafers sometimes are composed of an epoxy material, which may absorb moisture. The absorption of such moisture can result in relatively large dimensional changes to the wafer, which can negatively impact the optical performance of the assembly.